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1.
New Zealand is committed to developing sustainable forest management practices as evidenced through Government involvement in international forestry agreements such as the Montreal Process, and the forestry sector's adoption of forest certification mechanisms. Despite this, there is little quantitative evidence of how plantation forestry affects site quality and long-term site productivity. To address this issue, a nationwide study of site quality was established at 31 key sites covering the range of edaphic and environmental conditions for New Zealand plantation forests. At each location, eight short-term site quality plots were planted at a very high stand density (40,000 stems ha−1) to rapidly identify key soil indicators of growth which may be useful for determining site sustainability. The plots at each site were arranged in a factorial design with the following three factors: species (Pinus radiata D. Don and Cupressus lusitanica Mill.), fertiliser (no fertiliser and nutrients supplied in excess of crop demands) and disturbance (low and high disturbance). These plots were harvested after 4 years and data was used to (i) examine treatment and site effects on volume mean annual increment (MAI) and (ii) identify key soil properties that influence volume MAI for the two species.Volume MAI significantly ranged 7-fold across sites. For the treatments, species accounted for most of the variance in volume MAI, with values for P. radiata significantly exceeding those of C. lusitanica by 95%. Volume MAI was significantly affected by fertilisation which induced gains of 33%. Disturbance did not significantly affect volume MAI. After correction had been made for climatic variables, soil properties that were most strongly related to volume MAI for both species included C:N ratio, total phosphorus (P), and organic P. When soil properties were included in combination, the best predictive models of volume MAI formulated for P. radiata included total P and C:N ratio while the best predictive model for C. lusitanica included C:N ratio and Olsen P. Variation in species sensitivity to total P and C:N ratio is likely to be attributable to their different mycorrhizal associations. For both species, the most important soil physical property influenced by management operations was total porosity. This research suggests that total P, C:N ratio, Olsen P and total porosity should be used as indicator properties for determining sustainability of plantation grown P. radiata and C. lusitanica.  相似文献   

2.
We investigated the seasonal patterns of soil phosphorus (P) fractions under five vegetation types – Ulmus macrocarpa savanna, grassland, Pinus sylvestris var. mongolica plantation, Pinus tabulaeformis plantation, and Populus simonii plantation – in the southeastern Keerqin Sandy Lands of China. The measured P fractions (0–20 cm depth) included: soil total P (TP), total organic and inorganic P (TPo and TPi), bicarbonate extractable organic and inorganic P (BPo and BPi), microbial biomass P (MBP), and in situ resin-adsorbed P (resin-P). Soil TP and TPo concentrations in the savanna and grassland were significantly lower in summer than in spring and autumn. However, they were relatively stable in three forest plantations. Soil labile P fractions showed a significant seasonal pattern under all vegetation types with the peak in summer, except soil MBP that was constant in the savanna and grassland and BPo that decreased over time in the savanna. This pattern of labile P fractions was attributed to a combination of seasonal climatic changes, low P availability, as well as the biological controls of soil P transformation in the study area. Litter decomposition played a key role in soil P availability. The monthly resin-P released from litter decomposition in summer was 2.6–7.4 times greater than in other seasons, and was 1.7–3.4 times of that in the 10 cm depth soil. Concentrations of soil P fractions were obviously affected by vegetation type. The savanna had the highest total P and MBP concentrations and the P. tabulaeformis plantation had the highest BPi and resin-P among all vegetation types. Among forest plantations, P. simonii plantation had the highest total P and MBP. These results suggest that U. macrocarpa savanna is the best system conserving soil nutrient (particularly P) stocks and microbial activity, followed by the grassland and P. simonii plantation, while the pine plantations are the worst.  相似文献   

3.
Forest soil measurements were made at over 180 sites distributed throughout the H.J. Andrews Experimental Forest (HJA) in the Oregon Cascade Mountains. The influences of both elevation and aspect on soil variables were measured in the early (1998) and late summer (1994). Increased elevation significantly increased soil moisture, mean annual precipitation, soil organic matter, labile C and mineralizable N, microbial activities, extractable ammonium, and denitrification potentials. In contrast, bulk density, pH and soil temperature (1998 only) were significantly lower at the higher elevations. Relative to labile C, mineralizable N was preferentially sequestered at higher elevations. Aspect significantly affected annual mean temperature and precipitation, soil moisture and temperature, soil organic matter, mineralizable N, extractable ammonium, denitrification, and microbial activities. There were no significant higher statistical interactions between elevation and aspect on climatic or soil factors. Soil organic matter (SOM) accumulation at higher elevations is likely driven by a reduction in decomposition rates rather that an increase in primary productivity, however, SOM accumulation on north facing slopes is probably due to both a decrease in decomposition and an increase in primary production. Models of climate change effects on temperate forest soils based on elevational studies may not apply to aspect gradients since plant productivity may not respond to temperature–moisture gradients in the same way across all topographical features.  相似文献   

4.
Soil CO2 efflux (SR) is the second largest carbon flux on earth. We investigated the driving factors of the seasonal change and short-distance spatial variation in SR in a short-rotation plantation of willow (Salix viminalis Orm). Total annual SR ranged from 723 to 1149 g Cm(-2) year(-1). Both an exponential and a logistic model were fitted to the data, with soil temperature at a depth of 5 cm as the independent variable. The R2 values for individual sampling points ranged from 0.83 to 0.95 and from 0.85 to 0.93 for the exponential and logistic models, respectively, indicating that soil temperature largely determined the seasonal variation in SR. Modeled soil SR at 10 degrees C ranged from 1.22 to 1.95 micromol m(-2) s(-1), whereas modeled annual Q(10) values were between 3.31 and 6.13. These high Q(10) values were attributed to the absence of drought during the study in 2005. When the coefficients of the general SR models were replaced by linear dependencies on soil and vegetation-related characteristics, the resulting spatially explicit exponential and logistic SR models explained 85 and 86%, respectively, of the variability within the dataset. The analysis indicated that soil carbon concentration, leaf area index, soil pH and root biomass caused differences in SR at the short distances considered in this study. However, incorporating information on variables considered to account for spatial variability in the model did not result in a higher R2 compared with a simple temperature function. When the general SR models were applied to independent datasets from the same plantation, the logistic model provided a better fit than the exponential model when drought occurred. Drought greatly reduced the annual Q(10) values of SR.  相似文献   

5.
Myers BJ 《Tree physiology》1988,4(4):315-323
Water stress integral (S(Psi)), the cumulative integral of pre-dawn leaf water potential over any chosen period of time, was estimated from measurements of pre-dawn water potential made every two weeks in a Pinus radiata D. Don plantation near Canberra, Australia. Also measured were final length of current-season needles and annual stem basal area increment. Data were gathered over a 4-year period from a control plot, a fertilized plot, an irrigated plot, and two plots that were both fertilized and irrigated. Among years and treatments, annual basal area increment varied over a threefold range. Of this variation, 91% was accounted for by variation in S(Psi) for the entire year, during every month of which stem diameter growth occurred. Of variation in annual needle elongation, 90% was accounted for by variation in S(Psi) from late August to late February, which was the period of needle growth. In dry years, the annual value of S(Psi) in non-irrigated plots was mainly determined by soil water content, but in wet years in non-irrigated plots, and in all years in irrigated plots, it was closely correlated with tree nutrient status (r(2) = 0.81).  相似文献   

6.
Soil and climatic conditions for optimizing aboveground biomass yields of bioenergy short rotation coppices (SRCs) of Salix are not well elucidated. The objective of this study was to identify and quantify the limitations induced by soil and climate, and compare the magnitude of their effects, on annual aboveground yields across ten SRCs of Salix miyabeana SX67 in Quebec, Canada. The effects of weather variation between years on yields were also tested within locations. In five plots per SRC, soil bulk density, particle size, exchangeable cations and bulk composition were analysed, and moisture deficits were estimated using leaf δ13C. For each location, numerous weather variables were simulated for spring, summer and the whole growing season. Climate was calculated by averaging weather variables for growing seasons for which annual yields were available. Annual aboveground biomass yields were modelled using linear regression, partitioning of the variance and mixed models with soil, weather and climate variables as predictors. Across SRCs, silt content, soil organic matter, pH, exchangeable Ca and Mg, and total N and Zn were significantly and positively related to aboveground yields (adj. R 2 ranging from 0.38 to 0.79). Generally, annual yields were negatively related to summer temperature within SRCs (adj. R 2 = 0.92) and drought across SRCs (adj. R 2 = 0.54). Partitioning of the variance revealed that soil variables (~80%) had a greater effect on productivity than did climate variables (~10%). In fact, soil properties buffered or exacerbated water shortages and, thus, had a preponderant effect on yield.  相似文献   

7.
Digital terrain modeling and spatial climatic data have been used to estimate the spatial distribution of Japanese cedar (Cryptomeria japonica D. Don) forest productivity on a regional-scale. The study was conducted on Japanese cedar forests in Himi city, Oyabe city, Takaoka city, and Imizu city (a total area of 683 km2) in northwestern Toyama Prefecture. On the basis of data from 146 sample stands, above-ground net primary productivity (ANPP) was calculated from tree height, age, and density using existing ANPP conversion equations for Japanese cedar stands. Six topographic factors (slope, profile curvature, plan curvature, openness, wetness index, and topographic radiation index) were calculated from a 10-m cell size digital elevation model. Three climatic factors (annual mean temperature, annual total precipitation, and annual maximum snow depth) were obtained from an existing spatial data set. Relationships between ANPP and environmental factors were analyzed by regression tree models. For the tree model with ANPP as a dependent variable, four environmental factors (annual mean temperature, wetness index, openness, topographic radiation index) were adopted as independent variables. Annual mean temperature was the first split variable in this model and explained 25.5% of the total deviance in ANPP. Wetness index, which represents soil moisture variation caused by lateral flow, explained 11.5% of the total deviance in ANPP. The resulting tree model explained approximately half of the total deviation in ANPP and indicated that the spatial distribution of Japanese cedar productivity was controlled by regional-scale interactions between climatic and topographic processes. A high-resolution map of productivity was prepared by use of the ANPP prediction model and vegetation information obtained from satellite data.  相似文献   

8.
研究湿地防护林水文生态效益与气候环境因子的响应是湿地生态保护与经营管理中的热点问题。本文通过自然降雨径流小区定位观测试验,定量研究了黄河三角洲湿地刺槐林地及其采伐迹地的产流产沙效果和土壤水分动态变化规律。刺槐林地与采伐迹地相比,一场降雨的径流量减少53.9%～150.8%,泥沙量减少172.8%～387.1%;刺槐林地降雨径流洪峰峰值比采伐迹地低0.8L·s-1,且径流洪峰值出现的时间比采伐迹地滞后25min;刺槐林地和采伐迹地土壤含水率随年内降水量变化分干湿两季,呈周期性变化,刺槐林地年平均含水率比采伐迹地高23.3%～25.6%,特别是雨季其含水率比采伐迹地高24.3%～29.8%。应用逐步回归分析理论和方法,建立了刺槐生态防护林高生长量与气候环境因子的回归模型,影响该地区刺槐林高生长的主导因子是光照因子,其次是水分因子,再次是热量因子。该项研究可为黄河三角湿地刺槐防护林的更新改造及其生态水文效益的定量评价提供科学依据。  相似文献   

9.
An investigation of seed germination and early seedling growth ofEucalyptus microtheca was based on seed collection from 10 widely separated provenances in Australia. Genetic variation of seed germination and early seedling growth was observed among a series of provenances whose natural habitats range from different climatic condition. In the ten provenances, both the model of seed relative germination percentage and the model of seed total germination percentage fitted Logistic regression [y=a/(1+exp(-ex+b))]. In comparison with provenances from four high temperature (mean annual maximum temperature >30.0 °C; mean annual minimum temperature >17.0 °C) areas, six low temperature (mean annual maximum temperature <30.0 °C; mean annual minimum temperature <17.0 °C) areas showed the fast germination rate and the high total germination percentage. For each provenance we have 45 seedlings equally divided into three watering levels (100%, 50%, and 25% of field capacity), and studies on relationship between early seedling growth and climatic factors of the natural habitat of provenance. In control treatment, height growth of the seedling has been associated with intrinsically the driest quarter precipitation in the seed collection areas of provenance. In all the treatments, length growth of the biggest leaf of the seedling was related to mean annual maximum temperature and mean annual minimum temperature in origin of provenance. In contrast, basal diameter growth of the seedling was related to mean annual minimum temperature of the seed collection areas in water stress treatment. From an ecological viewpoint, the fast germination rate and the high total germination percentage of the seed and rapid early growth of the seedling appear to be favourable adaptations to the climatic conditions prevailing in the natural habitat of provenance. Responsible Editor: Chai Ruihai  相似文献   

10.
During 2005–2007, we used the eddy covariance and associated hydrometric methods to construct energy and water budgets along a chronosequence of loblolly pine (Pinus taeda) plantations that included a mid-rotation stand (LP) (i.e., 13–15 years old) and a recently established stand on a clearcut site (CC) (i.e., 4–6 years old) in Eastern North Carolina. Our central objective was to quantify the differences in both energy and water balances between the two contrasting stands and understand the underlining mechanisms of environmental controls. We found that the LP site received about 20% more net radiation (Rn) due to its lower averaged albedo (α) of 0.25, compared with that at the CC (α = 0.34). The mean monthly averaged Bowen ratios (β) at the LP site were 0.89 ± 0.7, significantly (p = 0.02) lower than at the CC site (1.45 ± 1.2). Higher net radiation resulted in a 28% higher (p = 0.02) latent heat flux (LE) for ecosystem evapotranspiration at the LP site, but there was no difference in sensible heat flux (H) between the two contrasting sites. The annual total evapotranspiration (ET) at the LP site and CC site was estimated as 1011–1226 and 755–855 mm year−1, respectively. The differences in ET rates between the two contrasting sites occurred mostly during the non-growing seasons and/or dry periods, and they were small during peak growing seasons or wet periods. Higher net radiation and biomass in LP were believed to be responsible to the higher ET. The monthly ET/Grass Reference ET ratios differed significantly across site and season. The annual ET/P ratio for the LP and CC were estimated as 0.70–1.13 and 0.60–0.88, respectively, indicating higher runoff production from the CC site than the LP site. This study implied that reforestation practices reduced surface albedos and thus increased available energy, but they did not necessarily increase energy for warming the atmosphere in the coastal plain region where soil water was generally not limited. This study showed the highly variable response of energy and water balances to forest management due to climatic variability.  相似文献   

11.
Changes in biomass and soil carbon with nitrogen fertilization were simulated for a 25-year loblolly pine (Pinus taeda) plantation and for three consecutive 7-year short-rotation cottonwood (Populus deltoides) stands. Simulations were conducted for 17 locations in the southeastern United States with mean annual temperatures ranging from 13.1 to 19.4 °C. The LINKAGES stand growth model, modified to include the “RothC” soil C and soil N model, simulated tree growth and soil C status. Nitrogen fertilization significantly increased cumulative cottonwood aboveground biomass in the three rotations from a site average of 106 to 272 Mg/ha in 21 years. The equivalent site averages for loblolly pine showed a significant increase from 176 and 184 Mg/ha in 25 years with fertilization. Location results, compared on the annual sum of daily mean air temperatures above 5.5 °C (growing-degree-days), showed contrasts. Loblolly pine biomass increased whereas cottonwood decreased with increasing growing-degree-days, particularly in cottonwood stands receiving N fertilization. The increment of biomass due to N addition per unit of control biomass (relative response) declined in both plantations with increase in growing-degree-days. Average soil C in loblolly pine stands increased from 24.3 to 40.4 Mg/ha in 25 years and in cottonwood soil C decreased from 14.7 to 13.7 Mg/ha after three 7-year rotations. Soil C did not decrease with increasing growing-degree-days in either plantation type suggesting that global warming may not initially affect soil C. Nitrogen fertilizer increased soil C slightly in cottonwood plantations and had no significant effect on the soil C of loblolly stands.  相似文献   

12.
Tree growth, water use, climate and soil water conditions were monitored over 12 months in two 3-4-year-old Eucalyptus urophylla S.T. Blake plantations on the Leizhou Peninsula of southern China. The Hetou plantation was established on a sandy soil of sedimentary origin with low water storage capacity, and the Jijia plantation was established on a clay soil formed on basalt. Sapwood area was approximately 50% higher at Jijia than at Hetou because of differences in plant spacing (1994 versus 1356 stems ha(-1)). Annual water use, assessed by heat pulse measurements, was 542 mm at Hetou and 559 mm at Jijia, with mean sap flux densities of 2772 and 1839 l m(-2) day(-1), respectively. Limitations to water use, imposed by climatic and soil factors, were quantified by analysis of daily canopy conductance in relation to daytime vapor pressure deficit (VPD) and soil water content. Similar annual water use at the two sites was a result of higher VPD and soil water availability at Hetou compensating for the greater sapwood area at Jijia. Potential annual water use in the absence of soil water limitation was estimated at 916 mm at Jijia and 815 mm at Hetou. Higher water availability during the dry season and early wet season at Hetou than at Jijia was the result of deep root systems. The results imply that water use by plantations on soils with high water availability and in areas of high VPD may be reduced by establishment at wider spacing. The environmental cost of water use by plantations must be weighed against their economic and environmental values to determine an appropriate mix of forestry, agriculture and other land uses in regions where water resources are limited.  相似文献   

13.
在孟加拉吉大港丘陵地区,调查了热带季风气候条件下的3种人工林(7年生大叶相思(Acacia auriculiformis)林、15年生大叶相思林和18年生混交林)和1种天然林的森林凋落物及其对土壤性质的作用.结果表明,总的有机质积累随人工林树龄增加而增加,但是年积累量随之降低.在同一植被类型内,不同坡位新鲜或部分分解的凋落物有机质累计量变化较大,坡底部有机质积累量最高,沿着山坡向上逐渐减少.在15年生大叶相思人工林内,土壤整合有机物积累量变化趋势与新鲜或部分分解有机质积累量变化趋势相反.在7年生和15年生的大叶相思林以及18年龄的阔叶混交人工林内,新鲜、部分分解和完全分解(含土壤整合有机质)有机质总生产速率分别是2554.31、705.79和1028.01kg.ha-1·a-1,新鲜凋落物有机质在3种林分中的生产速率分别是38.23,19.40和30.48 kg·ha-1·a-1.3种人工林和自然林内,平均新鲜凋落物的有机质积累占有机质产出总量的32.45%,部分分解凋落物占13.50%,而全分解整合土壤有机质占54.56%.森林土壤酸度随凋落物分解阶段的深入而增加.  相似文献   

14.
Soil loss rates currently recorded in forests are very low. Nevertheless, that may not be the case during stand installation and early tree growth stage, when soil is disturbed and scarcely covered. Site preparation techniques, performed to improve soil conditions for plant growth, should help reducing this erosion potential. In this study, several site preparation techniques were applied prior to installing a mixed stand (Pseudotsuga mensiezii and Castanea sativa) and a subsequent monitoring scheme of run-off and soil loss ran for 2?years in order to compare their effectiveness for erosion control. The experimental area, near Macedo de Cavaleiros, NE Portugal, at 700?m elevation, with annual means of 656?mm rainfall and 12°C temperature, has Mediterranean climatic conditions. Experimental design comprised three blocks, corresponding to different topographical positions (near flat plateau, moderate slope shoulder and steep mid-slope), where eight treatments were randomly distributed in plots with 375?m2 area: (1) Original soil control (no intervention on the original abandoned field); (2) No subsoiling, no ploughing, plantation with hole digger; (3) Subsoiling over the whole area, with covering shovel; (4) No subsoiling, contour bunds shaped by two plough passes; (5) Subsoiling in future plantation rows, contour bunds shaped by two plough passes; (6) Subsoiling over the whole area, contour bunds shaped by two plough passes; (7) Subsoiling over the whole area, contour ploughing over the whole area; and (8) Potential erosion (subsoiling over the whole area, ploughing downhill). Sediment and water exported from small plots (2.5?m2 average area), two replicates per treatment and block, were collected after each rainfall erosion event, in a total of 21, summing 1,876-mm precipitation in 2?years. Mean annual run-off and soil loss in the original soil were 3.4?mm and 11.6?g?m?2, respectively. In treatments 2–7, values were higher 3–7 times, for run-off, and 5–12 times, for soil loss. Potential erosion averages 2.3 t ha?1 year?1. Soil loss and run-off tend to increase with tillage intensity associated with site preparation technique, even though average two-year losses, in all cases, are below tolerable rates. Soil loss and run-off rates decreased with time, becoming globally negligible after 2?years. Slight and moderate soil disturbance intensity site preparation techniques reduce erosion rates to 30% of potential erosion, halving the critical period when above tolerance rates may occur.  相似文献   

15.
短轮伐期桉树人工林土壤温度特征分析   总被引：1，自引：0，他引：1       下载免费PDF全文
Based on the data collected from 2008 to 2010 in Eucalyptus plantation of Gaoyao city, Guangdong Province, the annual variation, seasonal variation and daily variation of soil temperature before and after rotation were analyzed. The result showed that the soil temperatures of various layers had a significantly positive correlation with the surface temperature. The annual variation of soil temperature showed a unimodal distribution and the annual amplitude became smaller in deeper layer. The daily variation followed a sinusoid and the daily amplitude became smaller in deeper layer. The peak value appeared later with the increasing of soil depth. The annual amplitude of the soil temperature in 2009 after the rotation (13.58 ℃) was smaller than in 2008 before the rotation (15.37 ℃). The peak value time appeared 1 hour ahead and the daily amplitude increased.  相似文献   

16.
The 2002 Biscuit Fire burned at mixed-severities encompassing over 200,000 ha of publicly owned forestland, including more than 8300 ha of conifer plantations. We used pre- and post-fire digital aerial photography to examine how the level of canopy damage varied within these plantations in relation to topography, weather, vegetation-cover, and management history, with an emphasis on the age of the plantation. We examined 198 plantations that varied widely in age (5-47 years), size (1.25-47 ha), and landscape context. The average level of canopy damage within the plantations was 77%. Based on Random Forest variable importance values, plantation age was the best predictor of canopy damage. Average annual precipitation, elevation and topographic position were ranked second, third, and fourth, respectively. A model selection procedure, using geo-statistical regression models and Akaike’s information criterion, corroborated the importance of plantation age relative to the other predictors tested and also suggested that the influence of age varied over time. The top ranked regression model indicated that the level of canopy damage reached its maximum around age 15 and stayed relatively high until age 25 before declining.  相似文献   

17.
We examined the relationships between Sitka spruce (Picea sitchensis (Bong.) Carr.) site index, windspeed, former land use, soil moisture and soil nutrients with a view to identifying factors limiting the growth potential of the species in three climate regions in Ireland. We selected plantations covering three climate regions (delineated on the basis of ‘growing season’ balance of precipitation and potential evapotranspiration; representing dry, moist and wet climate regions) located on sites representing the range of soil moisture regimes (SMR), soil nutrient regimes (SNR), and land use types found throughout Ireland. Site index of Sitka spruce varied among climate region, with significantly lower site index associated with the wet climate region mainly due to the deterioration in edaphic conditions and adverse climatic conditions. The effect of edaphic variables (SMR, SNR) on site index was consistent across climate regions, site index increasing with increasing SNR, and decreasing with excess moisture or moisture deficit. Site index reached a maximum on fresh/very rich sites in the dry and moist climate regions and on moist/rich sites in the wet climate region. In the dry climate region, water supply (SMR) was the most important variable regulating growth, in wetter windier climates nutrient supply (SNR) was the most important factor, accounting for 69% of the variation in site index. The study has allowed region-specific recommendations to be made for successful plantation establishment in Ireland and for countries with similar climatic regions.  相似文献   

18.
岷江上游水源涵养林涵水能力综合评价   总被引：2，自引：0，他引：2  
森林－土壤系统的水源涵养功能因其组成的差异而导致降水截留、蓄水、径流的变化。作者根据这一规律，以搜集、调查岷江上游水源涵养林的林冠截留量、地表枯落物蓄水量、苔藓层蓄水量、土壤孔隙蓄水量、土壤不透性能，土壤降水贮存量等进行分析，并赋与没森林植被系统中各组成成分以一定的得分，评价不森林－土壤系统的保水能力。评价结果表明四川西部天然林具有最强的保水能力，应进一步加强其保护工作，人为干扰严重的类型其保水能  相似文献   

19.
闫德仁  陈景莲 《林业研究》1999,10(4):239-242
IntroductionThesoildegradationofaFtificialforestisthecoreofresearchforplantationtostabilityandafforestationinChina.lnrecentyears,studiesonsoilfertiIityofplantationshavegradua[Iyincreased.forChinesefir,massonpine,popIar,Iarch,etc.Manyspecificmeas-ureshavebeenputfotwardtomaintainthesoilfertil-ityIevelinaFtificialforest(Pan1997,Yan1997lYan1996).owingtovariabilityofsoilfertilityinplantation,ithasmanydifficuItiestostudythesoiIfertility.Forexample,thesoiIsampIeplothastobemovedhori-zontalIyino…  相似文献   

20.
In the present context of global climate changes and the continuous development of forest management strategies based on the concept of sustainable use, it is important to develop a better understanding of the climatic factors controlling the growth of boreal forests. In this study, we report the results of a five-year field research within which day-to-day balsam fir (Abies balsamea (L.) Mill.) stem diameter variation was measured with dendrometers and examined in relation with various daily climatic variables. A model built with data from three growing seasons that included solar radiation, relative humidity, temperature and precipitation explained 84% of the variance in day-to-day stem diameter variation from June to September. The model has approximately the same predictive capability when validated with independent daily data from two other growing seasons. The model captured both the cumulative increment associated with the irreversible growth and the high frequency variation of day-to-day fluctuations associated to changes in the stem water content. In general, rainy days during which relative humidity was high and solar radiation was low favored stem diameter expansion (growth and swelling) while stem diameter decreased during periods of low relative humidity and high solar radiation. Similar models were obtained when the June-September period was divided into two parts (June-July and August-September) to better represent the period during which most of the cumulative annual stem increment is observed (June-July). Inter-annual variation in stem growth computed from the modeled day-to-day variation in stem diameter was significantly correlated to the inter-annual variation in annual growth determined from tree core measurements over a 10 year period (p = 0.023). The model was notably able to capture a particularly poor growing year (2006) presumably due to a short-term heat stress period. Results suggest that the inclusion of daily data in growth-climate models may contribute to improve predictions of the potential tree growth response to climate by identifying particular climatic events that may escape to a classical dendroclimatic approach.  相似文献   

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